Surface reconstruction and interface formation in Si and GaAs

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Abstract
We investigated the effects of substrate surface reconstruction upon the interface formation between In and Ge overlayers and Si(111)2 × 1, Si(111)7 × 7, and GaAs(110) substrates. Photoemission spectroscopy with synchrotron radiation was used to monitor the evolution of the interface parameters—Schottky barrier height or band discontinuities—as a function of the overlayer thickness. All interfaces involving Si(111)7 × 7 substrates exhibited a characteristic evolution pattern with saturation at 1.4–1.8 monolayers coverage. The interfaces involving Si(111)2 × 1 substrates instead exhibited faster evolution saturating below a monolayer coverage with marked differences between individual cleaved surfaces. A similarly rapid evolution was observed for the interfaces involving GaAs(110) substrates. These results indicate that the spectrum of intrinsic surface states is different for Si(111)2 × 1 and for Si(111)7 × 7. In particular for Si(111)7 × 7 a large density of localized states exists near the Fermi level.

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